Method for heating coal or the like



Nov. 11,1930, F. PUENING 1,781,079

METHOD FOR I'H'I'IIIG' COAL OR THE LIKE Filed sept. s, 1927 a sheets-sheet 1 w EL Nov. 11, 1930. F, PUENlNG METHOD FOR HEATING GOAL 0R THE LIKE 5, 1927 8 Sheets-Sheet 2 Filed Sept EN EN, es mb .OWG

Nov. 11, 1930. F. PUENING METHOD FOR HEATING COAL OR LIKE Filed Sept.` 3, 1927 8 Shee'cs--SheekI 3 Nov. 11, 1930. A.

F.v PUENING METHOD FOR HEATING COAL OR THE LIKE Filed sept. 5. 1927 8 Sheets-Sheet 4 Nov. 1l, 1930. F. PUENING 1,781,079

METHOD FOR HEATING COAL OR THE LIKE Filed Sept, 3, 1927 8 Sheets-Sheet 5 Nov. 11, 1930. F. PUENING 1,781,079

METHOD FOR HEATING COAL OR THE LIKE Filed sept. s, 1927 Nov. 1l, 1930. F. PUENING METHOD FOR HEATING COAL OR THE LIKE Filed Sept.

5, 1927 8 Sheets-Sheet 7 NOV 11, 1930- F. PUENING METHOD FOR'HEATING COAL 0R THE LIKE 3, 1927 8 Sheets-Sheet 8 Filed Sept.

gnue'ntoz f Patented Nov. 11, 1930 UNrrlsDisquaresN i PATENT OFFICE FRANZ PUENING, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO THE KOPPERS COM- PANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF DELAWARE i METHOD FOR HEATING COAL OR THE LIKEl Application filed September 3, `19227. Serial No. 217,488.

The invention relates primarily to methods yfor conditioning coal for either high temperature or low temperature coking' and has particularrelation to a method for preheat-ing coal prior to its being charged into the colting ovens or other apparatus to be transformed into coke, and also relates to-such methods When employed for heating or heat treatment of other carbonaceous materials, as for instance shale.

The manufacture of coke for industrial purposes is carried out With greater facility and an improved quality of product is obtained when the charge of colting-coal is introduced into the ovens or other colting apparatus, Whether high temperature or 'low temperature, in a dry and heated condition and completely ldevoid of moisture. Various methods have been practiced for this purpose and involving the treatment of the raw or Wet coal in the storage bins to eliminate the moisture therefrom prior to its being introduced into the ovens.

The present invention contemplates circulation of hot coal for drying Wet coal, and a method for continuously removing the raw or Wet coal from the main storage bins, applying heat thereto to'raise the same to the desired pre-coking temperature and eliminating all moist-ure, and thereafter storing the preheated coal in position for rapid and convenient transfer to the ovens or other coking apparatus to be charged.

A further object of the invention is to provide a'niethod for simultaneously handling `the Wet and preheated coal and utilizing thev -heat stored in the latter for removing the moisture from the' Wet coal prior tofintroducing the latter to the heating chamber, thereby rendering it possible to more rapidly impart the desired heat to the coal and minimizing the possibility of blocking the apparatus an impairing its continuous operation a preponderance of moisture in the Wet coal.

A further object of the invention is to provide a method for preheating coking-coal in which the proportion of the dry coal With respect to the raw coal may be increased or decreasedconveniently While the material is being continuously conducted through the apdue to paratus therefor as such variations are required by operating conditions, and Without interrupting the continuous handling of the material.

A further object of the invention is to provide amethodfor continuously preheating coking-coal immediately adjacent,l the coke oven battery. and in such manner as not to interfere with charging the ovens with raw coal .from the storage bin when desired or when the preheating apparatus is shut down or inoperative. v

A further object of the invention is to provide a method for carrying out the improved process in an apparatus composed lof comparatively fevv elements arranged for rapidly, continuously and economically handling the raw and preheated coal prior to its being charged intothe ovens, Without care or attention on the part of the operators, said element-s ofthe apparatus being designed to be positioned adjacent the coke oven battery,l and utilized as incident to the coking of coal according to present methods and standards, Without requiring material alteration of the coking apparatus.

The invention utilization 'of Waste heat return from the stack flues` of the coal preheating apparatus, with a resulting economy in operation and lessening in heat intensity, but the invention is not limited to the particular heating means described and any desired heating means may be employed. y

With such objects in view, or any other advantages which may be incident to the use of the improvements, the invention consists in the method for carrying the same into effect hereinafter set forth or claimed, With the understanding that the elements constituting the various claimed combinations may be varied in proportions and arrangement Without departing from the nature and scope of the invention. lThe drawings and descriptive specification shown and describe, by Way of example, an adaptation .of the invention to a standard coke oven for high temperature coking, but the invention is also adapted for employment with low temperature coking `ovens or other apparatus.

further contemplates the` In order to make the invention more clearly understood there are shown in the accompanying drawings means for carrying the same into practical effect, without limiting the improvements,- in their useful applications, to the particular constructions which,

for purposes of exempli'iication, have been made the subject of illustration. In the said drawings Fig. 1 is a side view, largely diagrammatic in character, showing the elements for carrying out the improved process, positioned above a coke oven battery constituted of horizontally aligned coking retort ovens.

' Fig. 2 is a plan view of the same, also largely diagrammatic in character.

Fig. 3 is an end elevation of the structure illustrated in Figs. 1 and 2.v

Fig. 3a is a detail perspective view of one of the buckets 10a shown in Fig. 3, and illustrating equal or varied proportionsof wet and heated coal in one of the buckets.

Fig; 4 is an enlarged vertical sectional vlew of the coal preheater, said view being taken through the preheater chamber only on line 4 4 of Fig. 2.

' Fig. 5 is a horizontal sectional view on line 5 5 of Fig. 4.

Fig. 6 is a vertical sectional view on line 6--6 of'Fig. 4.

Fig. 7 is an'enlarged vertical sectional view similar to Fig. 4 and illustrating more clearly the structure at the lower portion of the preheater.

Fig. 8 is a horizontal sectional view on line 8-8 of Fig. 7, the discharger rotors being omitted. f v

Fig.'9 is an enlargedv detail vertical sectional view on line 9-9 o f Fig.'4.

Fig. 10 is a vertical sectional detall view, on line 10 10 of Fig. 4, to show more clearly the arrangement of slots 50 and 54b for the introduction of heating gases into the passage 51 in Fig. 4. 4

Referring to the drawings and wlth particular reference to Figs. l, 2 and 3,1 indi- Cates a coalv storage bin for contalning the coal to be'preheated. The bin 1 is located. in any desired position p with respect yto the oven battery l, but is preferably disposed above the'battery, and isillustrated` as bemg supportedby usual or preferred vertical frame standards or I-beams 2. As best seen inFig.

' 1 the storage bin is divided into .or consti-v f tuted of a plurality of contiguous sections 1b with or without interveningy partion walls,

each section terminating atl its'lower portion rin a tapered discharge hopper 3 having the is preferably provided with a horizontally disposed worm or screw conveyor element 4 v at or near the lower portion of the bin and ex tending transversely and for substantlally the width of the bin. Each conveyor element 4 is enclosed within a protective housing 5 having a superposed tapered hood GWhich serves to protect the conveyor from the' weight of wet coal within the bin. The hood members 6 are provided with a plualityof spaced apertures 6a controlled ,by slidable shutters or closures 6b and through the medium of which delivery by gravity of lwet j coal within the bin 1 to the conveyors 4 is controlled. The conveyors 4 are power driven from any preferred source. As illustrated in Fig. 2 a shaft 6 is provided which is driven from a gear 6d connected to the power source, said shaft having a plurality of worm elements 6e meshing with corresponding worm wheels on the outer ends of the shafts 61 of the conveyors 4.

The conveyors 4 extend through the front wall of the bin l and each conveyor terf minates above and discharges into a single longitudinal conveyor 7 discharges' into theV chute 8al and the arrangement of the latter is such that the material or coal carried by' the conveyor discharges into one end only of the elevator buckets 10.a and said material may by such arrangement constitute approximately one-half or less than one-half of the carrying capacity of said buckets, and is deposited as described at one side of the latter or in the left hand end as viewed in F ig. 1. The elevator 10 is designed to discharge at its upper' end into a .chute 11 in turn discharging into an upper horizontally disposed conveyor l2 and a second horizontally disposed conveyor 13 arranged at an angle to the conveyor 12. The arrangement is such that as viewed in Figs. 2 and 3, the contents of the left hand ends or corners of the elevator buckets 10a are discharged into the conveyor 12, and the contents or a portion of the contents of the right hand Iends or corners'of said elevator buckets discharge into the conveyor 13. The conveyor elements 12 and 13 are enclosed within suitable protectivehousings 14 and 15. The

.intermediate portion of the screw conveyor 12 l" l communicates with an inclined chute 16 whlch in turn communicates with the upper ends of a plurality of vertically disposed vspaced preheater tubes or conduits 17. The

latter are contained within a heating chamber 18 (which has been omitted for clearness in Fig. 1), and the lower-ends of said tubes communicate with a pair of chutes or hoppers 19 and 19a (Fig. 1) forming an enclosing housing and having restricted portions in which are mounted on two parallel shafts 35 and 36 a plurality of spaced discharger rotors 20, 20a. A horizontally disposed transverse screw conveyor 21 is enclosed within a protective housing 22 and is designed to receivev the material from the discharger rotors 20, 20a, and convey the same to an inclined chute 23 communicating at one end with the discharge end of the conveyor 21 at the forward end of its housing, said chute communicating at its lower end with the elevator housing 9, and designed to discharge into the right hand ends or portions of the elevator buckets 10a. Any'surplus material which is not discharged by the conveyor 12 into the chute 16 is carried to the inner end of said conveyor and discharged into an inclined overflow chute 24 and thence returned by gravity and by vertical branch chutes 25 to points adjacent the transverse screw conveyors 4 in thel main storage bin 1 (Figs. 1 and 2).

The inner end of the angularly disposed horizontal conveyor 13 communicates with and discharges into the upper reduced portion 13a of a hot coal bin 26 which, similar to the bin 1, is preferably constituted of a plurality of contiguous aligned sections, each having a lower hopper portion 27 provided with a suitably controlled discharge orificev 28. The hotcoal bin 26 is supported in any desired or preferred manner as by vertical supports or I-beams 26a, adjacent the preheater tubes 17 and above the coke oven battery. The discharge orifices 28 of the hoppers 27 are designed to discharge into corresponding charging openings 34 of a larry car 29, having flanged wheels 30 and a plurality of hoppers or compartments 31, each of the latter being provided with a reduced discharge portion of nozzle 32. lThe larry car 29 travels u on rails 33 laid longitudinally on the top o the oven battery and is designed f to discharge its contents through the reduced nozzles 32 into the usual charging doors (not shown) at the top of the various ovens of the battery.

As best seen in Figs. 4 and 5, the preheater tubes 17, of sheet metal, are or may be arranged in two (or more) spaced apart palrs of closely spaced rows within the heating chamber 18 and in alternate or staggered relation. This design and arrangement of the tubes obtains a minimum area of the heatmg chamber with a maximum of tubes of relatively small diameter, as well as convenience in the arrangement and operation of the d1scharger rotors 20, 20B. The latter are keyed as 20b on the two parallelshafts 35 and 36 respectively journaled in the reduced intermediate portions 37 and 38 of the hoppers or chutes 19 and 19a, and one rotor 2O or 20a is provided for and beneath each of the stag- -gered tubes 17, to insure a uniform flow through each tube. The preheated coal discharged from both pairs of staggered tubes is conducted by the chute 39, beneath the discharger rotors, to the conveyor 21.

As best seen inFigs. 4, 7, 8 and 9, the discharger rotors 20, on shaft 35 extending longitudinally of the preheater, are disposed within the restricted portion 37 of the hopper or chute 19 and take care of the discharge from the two left hand rows of preheater tubes 17. The discharger rotors 20a on vthe companion shaft 36 are disposed within the restricted portion 38 of the hopper or chute -19a and take care of the discharge from the right hand rows of preheater tubes 17 The rotors 20, and 20al are suitably spaced as by collars 40 on their respective shafts 35 and 36 in such manner that one rotor is provided beneath and takes care of the discharge from each preheater tube 17. Or the rotors may be long enough to extend under several or many of the preheater tubes 17. Suitable partition walls 41 are provided within the chutes 19 and 19a to direct the discharge from the tubes to their respective rotors, said partition walls being apertured as at 42 (Fig. 9) to provide clearance for the shafts and rotors when the apparatus is assembled. The chutes 19 and 19a may be removably secured to the bottom of the preheater chamber 18 as by bolts or rivets extending through aligned apertures 43 in the respective elements (Fig. 7). A suitable intermediate fluid tight packing 44 may be provided to insure against the escape of heating gases from within the chamber 18. As best seen in Fig. 4 the outer enclosing chute 39 rmay be bolted or otherwise secured to longitudinally extending channel beams 45 which serve to support the preheater structure above the coke oven battery. The top portion or walls of the contiguous chutes 19, 19a may consist of one or more aligned metallic castings 46 and 47 having apertures 48 therein corresponding in number and arrangement to the tubes 17 and through which apertures 4the preheated coal is discharged from said tubes into the bottom portion of said chutes or hoppers 19 and 19B. The apertures 48 are or may be extended at one side to facilitate the discharge of heated material from the tubes toward their respective discharger rotors, it being noted that the left hand row of tubes of each pair as seen in Figs. 7 and 8, discharges toward the right hand, and the right hand tube of each pair discharges toward the left.

rlhe heating medium for externally heating the tubes 17 within the chamber'18 consists of combustion gases from any convenient fuel such as gas, oil, coal or coke. Referring to Figs. 4 and 5 the fuel, for instance gas, with air, is admitted to the combustion chamber 49a primarily through the port 49 and injector burner 49h, and after combusthe coal-fusing point, depends on the kind of coal and other factors. When employing waste gases from the ovens it is apparent, from the temperature of those gases and their heat content, that the coal can be preheated by them to only a temperature slightly in excess of dryness.

In this connection it will be observed that the several tubes 17 are of relatively small diameter as compared to their longitudinal dimensions, which results in the coal being evenly and thoroughly heated during its passage through the tubes by means of the heat within the chamber 18, and all moisture is dispelled from the coal. The heated coal collects in the chutes or bins 19 and 19a, and the coal from each tube is fed downwardly by means of its individual discharge rotor 20, 20a, the rotors being rotated on their shafts 35 and 36 by any appropriate power source. These rotors determine the speed of movement of the heated coal through the tubes. The heated coal is received by the transverse conveyor 21 and conveyed forwardly thereby and discharged into the chute 23 and thence into the right hand por? tions of the endless conveyor buckets 10a within the elevator housing 9. These buckets which are still receiving wet coal in their left hand portions from the bin 1 in the manner described, now carry upwardly separate and individual charges of wet and vdry coal- (see dotted line in elevator buckets in Fig. 1). During their upward travel within theelevator housing the raw or wet coal charge is subjected to an initial heat from the charge of hot coal carried by the same bucket, and the heating up of the wet coal is continued and intensified when both coals enter the upper transverse conveyor 12 in which they are thoroughly mixed, so that the moisture in the wet coal is speedily evaporated and, when the mixture enters the preheater tubes through the chute 16, caking in the tubes is avoided.v I

The wet coal and dry coal which are bemg mixed in the big top conveyor 12 may not find time enough to evaporate all the moisture contained in the wet coal, by virtue of contact with hot coal. This question of time merely depends on the size of the conveyor 12 and the volume of coals passing through. In case all water in the wet coal is not evaporated, some wet coal or partially wet coal will enter preheater tubes 17. This however is not objectionable as long as the amount of dry hot coal present in the tubes 17, simultaneously with the wet coal, is so preponderant in amount and weight that the mixture of wet and dry after reaching equilibrium of temperature is of such degree of temperature that steam created from the wet coal cannot condense and formfa wet cake or clump. In other words, the mixture entering the tubes must be safely above 212 F. The

mixture of hot and wet coal which has been agitated in screw conveyor 12 is given certain room in which the water can evaporate before entering the tubes. This room consists in the chute 16 between screw conveyor`12 and tubes 17. By making this roomlarger additional time can be given. The one side wall 17a of this room is so positioned as to prolong the time that `the mixture of wet and dry coal stay in the conveyor 12, for better drying. before the coal can fall into the preheater tubes or conduits 17.

When the elevator buckets, each carrying individual charges of wet and heated coal, reach thelupward extent'of their travel, the wet coal which has been subjected to initial radiated and conducted heat from the hot coal charge, is conveyed to the top of the preheater tubes by conveyor 12 and chute 16 as above described. The individual charges of hot coal in the buckets are discharged into the upper horizontal conveyor 13 which diverges at an angle to the conveyor 12.- The hot coal is discharged by the conveyor 13 into the restricted portion 13a of the hot bin 26 and is stored therein until it is desired to charge the individual and contiguous ovens of a battery. At such time this preheated coil, which is entirely devoid of moisture and has the desired temperature in the hot bin, is discharged through the individually controlled apertures 28 of the bin into the corresponding compartments or hoppers 31 of the larry car 29. The latter isthen transferred along the rails 33 into position above any desired oven to be charged, and the preheated coal is discharged into the ovens through the discharge spouts 32 of the larry car.

The storage bin 1 lfor the raw or wet coal is of large capacity, relative to the hot coal bin 26, because preferably the big binv 1 is filled during the short day-labor shift with enough raw or wet coal forat least the whole twenty-four hour day continuous operation of the oven battery but the preheating apparatus is run continuously, so that the relatively small bin 26 is required to hold at any one time only enough coal for a fraction of the full days consumption, say six or eight hours; and thus not only is the preheated coal maintained always in the best condition for charging into the ovens but also there is avoidance of all danger that might be incident to keepingtoo great a bulk of heated coal in storage.

It will be observed that by the method and apparatus of the invention the respective ovens of the battery are provided with individual charges of preheated coal, which is a distinct economic advantage in the subsequent production or manufacture of coke in the ovens. The time required for coking is materially decreased and a product of higher quality is thereby obtained.

In the practice of the invention as thus far described, the wet coal is given but a Asingle passage through the preheater tubes.

In other words, as an example, o ne ton of wet coal is removed from the mam storage bin, andl elevated by the buckets 10'L to be dis- .charged into the conveyor 12 and thence 1nto the top of the preheater tubes, the coal occupying substantially one-half of the capacity `m of the elevator buckets. The preheated coal is again transferred to and elevated by the elevator buckets and discharged into the hot bin 26, the heated coal at this-time occupying substantially one-half of the capacity but in the opposite ends of the elevator uckets.

f The elevator 10 constitutes the only element of' the apparatus which handles two tons of coal per unit of time, namely one ton of wet coal in the left hand ends of Lthe buckets and one ton of dry coal in the opposite ends of said buckets.

' But the proportion which the wet coal bears .to thedry or preheated coal during the carryf .that the coal from the main storage bin is often so wet that it wouldtend to stick and failv to .enter the tops of and slide down through the preheater'tubes17. To remedy this, the number of revolutions of the discharger rotors 20, 20 and conveyors 12 and' 21 andthe speed of elevator 10 may be increased, with the speed or number of revolu- 'tions of transverse conveyors 4 and communieating longitudinal conveyor 7 remaining the same. Thisresults in the amount of wet coal removed from the main bin 1 remaining constant, or, as stated above, one ton of coal per unit of time:J However, the amount of coal passing through the preheater tubes or conduits has been increased to, for example, four tons per unit of time. The buckets 10a ofthe elevator will be filled at their left hand corners with one ton of wet coal and at their right hand corners with four tons of dry coal which latter has passed once through the pre-^` heater tubes 17. This preponderance of dry coal serves to increase the speed with which the wet coal is heated u and dried after it has been discharged at the top of the elevator and has been thoroughly mixed with the dry coal passing along the screw conveyor 12. This results in all moisture being evaporated from the wet coal prior to its being conducted to the top of the preheater tubes 17, thereby eliminating the possibility of the coal blocking and refusing to enter and slide through the preheater tubes. By. variations of the process described any proportion of wet and dry coal may be conducted through the preheater tubes, thereby rendering it possible 't0 reduce the diameter of the latter with resulting economies, as well as increasing the speed of travel of the coal .through the preheater.

This adaptability and adjustability of the method and apparatus therefor to various coals and to various degrees of moisture in the same coal, is one of the most important and useful aspects of the invention. f

It will be understood that the method herein described and claimed may be employed for the heating or heat treatment of carbonaceous materials other than coal. For instance, it may be adapted to and employed for not only the drying or preheating of other carbonaceous materials but also for the vheat treatment or distillation of such carbonaceous materials as shale. And it will be understood that in the claims hereinafter made the term coal is ernployed in a generic manner to indicate true coal or any of the various'related carbonaceous materials or such other carbonaceous materials as shale, or the like.

The apparatus herein described forms the subject-matter of my co-pending divisional application Serial No. 485,077 filed September 29, 1930.

This invention has been set forth as embodied and practiced in a particular example, but it is not limited thereto and may be variously embodied and practiced within the scope of the claims hereinafter made.

I claim i 1. The processof preheating coal for cok- Aing purposes, which consists in supplying coal and subjecting it to a preheating medium at a temperature in excess of 212 and ranging to substantially 600 Fahr., discharging the preheated coal, and utilizing the sensible -heat of the preheated coal within said temperature range for evaporating the moisture from wet coal being supplied for subjection to said preheating medium in advance of its subjection to said preheating medium.

2. The process of heating coal for coking or' like purposes, which comprises continu- -ously conveying moist solid coal from a supplythereof and subjecting it to indirect heat, continuously conveying the heated coal and collecting it, said heated coal during conveyance thereof being juxtaposed to said moist coal during conveyance thereof and prior to heating the latter, and separately discharging at least a portion of the heated coal before subjecting the moist material to the indirect heating.

3. The process of heating coal for coking purposes whichcomprises continuously withdrawing wet solid coal from a supply thereof and subjecting it to a heating medium, continuously discharging the heated coal, regulating the rate of discharge of the heated coal, and conveying heated coal along with the wet coal to be subjected to said heating medium for initially preheating the wet coal prior to subjecting it to said heating medium, and subjecting the preheated wet coal only to said heating medium.

4. The process of .heating coal for coking purposes, which comprises continuously withdrawing raw solid coal from storage and subjecting it to a heating medium, continuously and automatically discharging the heated coal from contact with said heating medium, and conveying and mixing the heated coal with the raw coal to be subjected to said heating medium prior to subjecting the raw coal only to said heating medium.

5. The process of heating -coal for coking purposes, which comprises withdrawing raw solid coal from storage and subjecting it to a heating medium, discharging the heated coal, regulating the rate of discharge of said heated coal, and simultanenously conveying along together various proportions of heated and raw coal to 4be subjected to said heating medium prior t0. subjecting the' raw coal only to said heating means, whereby agglomeration of said raw coal is prevented, and separately collecting the heated coal immediately after its .conveyance with said raw coal.

6. The process of heating coal `for coking purposes, which comprises conveying wet solid coal from storage and conveying it to a heating medium, discharging the heated -coal from'contact with said heating medium and conveying it along with fresh quantities has issued from the preheating stage and before new wet material enters the preheating stage, the amount of hot material removed from the cycle being equal to the amount of wet material admixed to the cycle.

9. A method of supplying preheated coal to a cokin'g battery, which comprises storing at relativel long intervals large volumes of raw coal, su stantially continuously withdrawing coal from such storage and preheating and delivering such coal into storage of relatively small volume, and at relatively short intervals constantly withdrawing such preheated coal from such small storage volume and charging it into the coking battery.

10. AThe process of heating coal for coking purposes which consists in supplying wet coal to a heating medium, discharging the heated coal from said heating medium and conveying the heated coal and moist coal simultaneously in varyingproportions to adjacent said heating medium, whereby to utilize the sensible heat of the heated .coal to evaporate moisture from the wet coal prior to its delivery to said heating medium, and diverting the conveyed heated coal only to a separate collection zone.

In testimony whereof, I have hereunto set m hand. A

y FRANZ PUENING.

of said wet coal being conveyed to said heating medium, and varying the relative speeds of the conveying means to simultaneously so convey predetermined proportions of wet and heated coal prior to subjecting the wet coal only to said heating medium, and separately collecting said heated material. j

7 A method of drying and lheating coal for coking or like purposes which comprises I mixing a unit of wet coal with such an amount of already preheated coal that the temperai ture of the mixture lies above the condensing point of water, whqereby a percentage of moisture in the wet coal unit is evaporated, d1-

' verting the partially evaporated wet coal from the moisture and passing the same through the preheater, and separately collecting the preheated coal which has been utlized to evaporate the moisture in the wet coal unit.

8. A method of heating coal or the like for coking or like purposes, which comprises establishing a closed cyclic path of travel for the carbonaceous material, this path .including a preheating stage through whlch the material passes in continuous rotation, admixing wet material to the continuously clrculating material at a point before 1t enters the preheating stage, whereby the temperature in the preheating stage and thev amounts of wet and dry material are so regulated that the temperature of the mixture is above the con- 

